The present invention relates generally to mycotoxin binders and, more specifically, to mycotoxin binders utilizing humic compounds.
Mycotoxins are invisible, odorless and cannot be detected by smell or taste, but can result in great economic losses at all levels of agricultural feed production and especially in animal production. Mycotoxins are secondary metabolites produced by filamentous fungi such as Fusarium, Aspergillus, and Penicillium prior to and during harvest, or during (improper) storage. Their toxic effects are very diverse (Akande, K. E., Abubakar, M. M., Adegbola, T. A., and Bogoro, S. E. 2006 Nutritional and Health Implications of Mycotoxins in Animal Feeds: A Review. Pakistan Journal of Nutrition, 5: 398-403). In farm animals, mycotoxins have negative effects on feed intake, animal performance, reproductive rate, growth efficiency, immunological defense as well as been carcinogenic, mutagenic, teratogenic, cause tremors or damage the central nervous system, hemorrhagic, as well as causing damage to the liver and kidneys. Mycotoxins are metabolized in the liver and the kidneys and also by microorganisms in the digestive tract. Therefore, often the chemical structure and associated toxicity of mycotoxin residues excreted by animals or found in their tissues are different from the parent molecule (Ratcliff, J. The Role of Mycotoxins in Food and Feed Safety. Presented at Animal Feed Manufacturers Association, Aug. 16, 2002). Various mycotoxins may occur simultaneously, depending on the environmental and substrate conditions (Sohn, H. B., Seo, J. A., and Lee, Y. W. 1999 Co-occurrence of Fusarium Mycotoxins in Mouldy and Healthy Corn from Korea. Food Additives and Contaminants, 16: 153-158). Considering this coincident production, it is very likely, that animals are exposed to mixtures rather than to individual compounds. Field studies have shown that more severe toxicosis in animals can result from the additive and synergistic effects of different mycotoxins (Ratcliff, 2002). The problem of mycotoxins does not just end in animal feed or reduced animal performance, many become concentrated in meat, eggs and milk of animal and can pose a threat to human health. There is increasing concern about levels of mycotoxins in human foods, both from vegetable origin and animal origin.
Although there are geographic and climatic differences in the production and occurrence of mycotoxins, exposure to these substances is worldwide. Mycotoxins are estimated to affect as much as 25 percent of the world's crops each year (Akande, 2006). Most countries have stringent regulation on mycotoxin levels in feed and the main goal of agricultural and food industries is the prevention of mycotoxin contamination in the field. Management practices to maximize plant performance and decrease plant stress can decrease mycotoxin contamination substantially. This includes planting adapted varieties, proper fertilization, weed control, necessary irrigation, and proper crop rotation (Edwards, S. G. 2004 Influence of Agricultural Practices on Fusarium Infection of Cereals and Subsequesnt Contamination of Grain by Tricothecenes Mycotoxins. Toxicology Letters, 153: 29-35). But even the best management strategies cannot eliminate mycotoxin contamination in years favorable for disease development.
Among the various mycotoxins identified especially affecting poultry, some occur significantly in naturally contaminated foods and feeds. They are aflatoxin; ochratoxin, zearalenone, T-2 toxin, vomitoxin and fumonisin. They cause detrimental effects on birds, such as growth impairment, immune depression, and paleness in broilers, which finally bring out economic losses.
Aflatoxin B1, a metabolite of fungus Aspergillus flavus and Aspergillus parasiticus, is an extremely hepatotoxic compound that frequently contaminates poultry feeds at low levels. Another family of mycotoxins produced by Penicillium and Aspergillus genera is ochratoxin. Ochratoxin, being the most potent toxin, adversely affects production parameters and the health of poultry. Ingestion of ochratoxin causes severe kidney damage. T-2 toxin induces severe inflammatory reactions and neural disturbances in animals and humans, whereas zearalenone appears to have no effect on poultry health and performance. Poultry rations with high levels of Fusarium contamination have been associated with poor performance, feed refusal, diarrhea, leg weakness, oral lesions, and/or high mortality.
The toxicity and clinical signs observed in animals when more than one mycotoxin is present in feed are complex and diverse. Mycotoxins are usually accompanied by other unknown metabolites which may have synergistic or additive effects. The ability of binders to alleviate the adverse effects of the several combinations of mycotoxins present naturally in feed on productivity and serum biochemical and hematological parameters remains yet to be explored.
Practical methods to detoxify mycotoxin contaminated grain on a large scale and in a cost-effective manner are not currently available. At present, one of the more promising and practical approaches is the use of adsorbents. However, several adsorbents have been shown to impair nutrient utilization (Kubena, L. F., R. B. Harvey, T. D. Phillips, D. E. Corrier, and W. E. Huff. Diminution of aflatoxicosis in growing chickens by the dietary addition of hydrated sodium calcium aluminosilicate. Poult. Sci. 69:727-735. 1990) and mineral adsorption (Chestnut, A. B., P. D. Anderson, M. A. Cochran, H. A. Fribourg, and K. D. Twinn. 1992. Effects of hydrated sodium calcium aluminosilicate on fescue toxicosis and mineral absorption. J. Anim. Sci. 70:2838-2846) and lack binding effects against multiple mycotoxins of practical importance (Edrington, T. S.; Sarr, A. B.; Kubena, L. F.; Harvey, R. B.; Phillips, T. D. (1996). Hydrated sodium calcium aluminosilicate (HSCAS), acidic HSCAS, and activated charcoal reduce urinary excretion of aflatoxin M1 in turkey poults. Lack of effect by activated charcoal on aflatoxicosis. Toxicology letter, 89: 115-122).
Zearalenone (ZEA) causes hyperestrogenism in swine when ingested at levels as low as 1 μg/g feed. Pathology in swine is more pronounced in prepubertal gilts and are characterized by tumefaction of the vulva, prolapses of the vagina and rectum and enlargement of the mammary glands. In cycling animals, effects of zearalenone include conception failure, pseudopregnancy and abortion. The metabolism of ZEA seems to occur essentially in the liver leading to α and β zeatalenol. The enzyme believed to catalyze reduction of ZEA to zearalenol is 3-α-hydroxysteroid dehydrogenase (3α-HSD). This enzyme is also known to degrade 5-α androstan-3,17-dione, a product of steroid hormone metabolism. As known in several studies, ZEA and its metabolites are excreted mainly via feces and urine. Swine are more sensitive to ZEA than other classes of livestock, and feeding regimens that minimize losses due to feed wastage and poor performance are desirable. Some compounds (i.e. fiber, formalin, sodium carbonate and monomethylamine) has been shown to protect against numerous xenobiotisc, including ZEA effects.
The use of mold inhibitors or preservation by acids can only reduce the amount of mold but does not influence the content of mycotoxins generated prior to treatment. If mycotoxins have been produced earlier they will not be affected in any form by mold inhibitors or acid mixtures, as they are very stable compounds. Thus these toxic compounds remain in the formerly infected commodity even if no further mold can be seen or detected. The most commonly used strategy of reducing exposure to mycotoxins is the decrease in their bioavailability by the inclusion of various mycotoxin binding agents or adsorbents, which leads to a reduction of mycotoxin uptake and distribution to the blood and target organs. Major advantages of adsorbents include expense, safety and the ease to add to animal feeds. Various substance groups have been tested and used for this purpose, with aluminum silicates, in particular clay and zeolitic minerals, as the most commonly applied groups.
Humic acids are ubiquitous and are found wherever matter is being decomposed or has been transposed, as in the case of sediments. They are natural components of drinking water, soil and lignite. Humic substances have a strong affinity to bind various substances, such as heavy metals, herbicides, different mutagens, monoaromatic and polycyclic aromatic compounds and minerals. Farmers use humates to accelerate seed germination and improve rhizome growth for many years (Islam, K. M., Schuhmacher, S. A., and Gropp, M. J. 2005 Humic Substances in Animal Culture. Pakistan Journal of Nutrition, 4: 126-134). The materials are able to stimulate oxygen transport, accelerate respiration and promote efficient utilization of nutrient by plants (Osterberg, R. and Mortensen, K. 1994 The Growth of Fractal Humic Acids: Cluster Correlation and Gel Formation. Radiation and Environmental Biophysics, 33: 269-276). These observations prompted scientists to study the specific properties of humates and their possible benefits in improving health and well being of humans and animals. Humic substances have been used as an anti-diarrheal, analgesic, immune-stimulatory and growth promoting agents in veterinary practices in Europe (Islam, 2005). Humic acids inhibit bacterial and fungal growth, thus indirectly decrease levels of mycotoxins in feed (Riede, U. N., Zeck-Keapp, G., Freudenberg, N., Keller, H. U., and Seubert, B. 2007 Humate Induced Activation of Human Granulocytes. Virchows Archives of Biology: Cell Pathology, 60: 27-34). Some humic substances and their salts have been described to directly interact with mycotoxins by their mycotoxin binding capacity (Sabater-Vilar, M., Malekinejad, H., Selman, M. H. J., Ven Der Doelen, M. A. M., and Fink-Gremmels, J. 2007, In Vitro Assessment of Absorbents Aiming to Prevent Deoxynivalenol and Zearalenone Mycotoxicosis. Micropathologia, 163: 81-90; Ye, S., Lv, X., and Zhou, A. 2009 In Vitro Evaluation of the Efficacy of Sodium Humate as an Aflatoxin B1 Adsorbent. Australian Journal of Basic and Applied Sciences, 3: 1296-1300; Jansen van Rensburg, C., Van Rensburg, C. E. J., Van Ryssen, J. B. J., Casey, N. H., and Rottinghaus, G. E. 2006 In Vitro and In Vivo Assessment of Humic Acid as an Aflatoxin Binder in Broiler Chickens. Poultry Science, 85: 1576-1583).